The invention is based on a disconnector according to the preamble of patent claim 1.
Such a disconnector is used within gas-insulated switchgear assemblies.
Disconnectors within gas-insulated switchgear assemblies (GIS) are dielectrically critical components since they have small radii and therefore cause inhomogeneities in the shape of the electric field.
A disconnector essentially comprises grounded encapsulation, two isolating contacts which are held, generally centrally, in the encapsulation by supporting insulators, and a moveable isolating contact finger. The isolating contact finger is arranged such that it can be moved between the isolating contacts. When the disconnector is open, the isolating contact finger is essentially located within one of the isolating contacts, so that the distance between the two isolating contacts forms the isolation gap. When the disconnector is closed, the isolating contact finger bridges the isolation gap between the two isolating contacts, and thus forms a conductive connection. During opening and closing of the disconnector, the isolating contact finger is moved in the direction of one isolating contact or the other, forming disconnector sparks, until the isolation gap is completely open or closed.
The encapsulation of conventional disconnectors is designed to be enlarged in particular in the region of the isolation gap in order to prevent a disconnector spark from flashing over to the encapsulation during the switching process. The encapsulation is generally in the form of a casting, which is complex and expensive to produce.
DE 1,131,771 discloses a disconnector in which a solid insulation coating is applied to the inside of the encapsulation. In order to prevent creepage currents from bridging the open disconnector along the solid insulation coating on the encapsulation, the solid insulation coating is interrupted in the region of the center of the isolation gap by a convex, grounded bead. In order to prevent any flashovers from the isolating contact finger to the grounded bead while the disconnector is being opened, an additional tubular insulation shield is provided, covering the bead.
The invention is based on the object of providing a disconnector of the type mentioned initially, which has high dielectric strength, and nevertheless is simple and compact, and can be produced cost-effectively.
According to the embodiments of the invention, the object is achieved in that the insulation coating is applied without any gaps to the inside of the encapsulation, at least in the region between the isolating contacts, and in that at least one projection is provided on the insulation coating. Firstly, this allows the distance between the encapsulation and the isolating contacts to be reduced, since the insulation coating prevents any discharge which is produced in the direction of the encapsulation during opening of the disconnector from reaching the encapsulation and leading to a heavy-current arc. Secondly, the projection on the insulation coating makes it possible to prevent the opened disconnector from being bridged by creepage currents along the solid insulation coating on the encapsulation.
More compact and cheaper disconnectors can thus be used for the same maximum electrical loads.